Fluid pressure control apparatus



E. DENNIS' Filed'Nov. 275, 1932 4 Shees-Sheet 1 Jan. 14, 1936.

FLUID PRESSURE c oN'PPoL APPARATUS 3MP-m l .nis I.

E. L. DENNIS FLUID PRESSURE CONTROL APPARATUS Jan.. 14, 1936.

Filed Nov. '25, 1932 4 Sheets-Sheet 2 Y WMFMW/ Jan. 14, 1936. l E. DENNIS FLUID PRESSURE CONTROL APPARATUS l L `4 Sheets-Sheet. 3

j'Filed Nov. 25 1932 if @fn Jah.' 145 1936. Y E. DENN|$ FLUID PRESSURE ,CONTROL APPARATUS Filled Nov. 25, 1932 sheets-sneer. 4

Patented Jen. 14,1936 f t Y 2,028,049 L UNITED STATES PATENT OFFICE FLUID Pnnssilmi ooN'rnoL APPARATUS Edwin L. Dennis, Reserve, La. Application November z5, 193g, serial No. 644,352 v ioolaims. (ci. 23e-72e) l This application is a continuation-inspart of Inrthe drawings:

my application, Serial No. 574,666,7led Novem- Figure 1iS an eleVatiOn 0f a CenSta-nt Pressure ber 12, 1931 for Automatic fluid pressure control. System embdying the ypresent inventien; 'I'he subject matter of this application is in the Figure 2 iS a fragmentary Side elevation 0f V5 nature of an improvement on the apparatus dispressure control apparatus' forming Dart 0f the 5 closed in the first named case, which has mapresent invention, the electrical elements thereof tured into United States Patent No; 1,914,682, being shown indiagram;y June'13, 1933. Figure 3 is a central vertical section through As in my prior application, the present invena Bourdon pressure gauge modified fOr use in l tion relates generally to apparatus for controlling this invention: 1Q 01' stabilizing fluid pressure 0r temperature by Figure 4 iS' a VltCal Section taken 0D. the means responsive to the pressure or temperature line 4-4 0f Figure 3; i to be controlled or stabilized. Specifically, the y Figure 5 iS a fragmentary Section taken 0n l invention relates to apparatus for controlling the the line 5--5 0f Figure 3;

pressure ortemperature in the steam chambers Figure 6 is a fragmentary eleVatiOn 0f Dart 0f 15 of boilers or the like, in which the apparatus is the dial 0f the Said pressure gauge; and i controlled in operation by changes of pressure Figure 7 iS a fragmentary diagram illustrat-A or temperature in salir chambers. f ins-e modication in the pressure gauge 0f this u The invention is of peculiar importance in the System, With a COrreSpOnding medleatiOn in sugar industry, in which the load is very'fluctuvthe C011t1'0l 1elaysi 20 i the boilers frequently change from 100% `rating ating. Instantaneous loadsashigh as 1500 horse As shown in Figure 1 0f the drawings. th power are thrown on or olf the line. Under hand v inVentiOIl iS adapted t0 be applied t0 a Steam control it has been found impossible to maintain generating System designated generally by the a pressure within a, fifteen pound range; 4and reference character I. This system, for the ,purpose of illustration, is assumed to be -oper- 25 to 200%, or reverse, in as short an interval as ated by gas under Pressure and Supplied from twelve minutes. It is, of course, desirable to mam 2 controlled py a' valve 3 The 2 maintain this pressure vas nearly constant as 1S connecte@ to one .S1deof a' safetyva'lve l to practicable. -f the otshr' Stdrcg Wmlllvs scoinigpg'sel fg 30 l pipe in w c a. v

ti Th aparatls dsclosedlmtny lno applca" feed pipe 5 is connected to a horizontalmain 1 on @s 526.11 Dun Capab e m, at," ua prac me 'extending vtoward the generating-system I and 91: mamtaufmg the pressure Wlthm one pound terminating in a valve controlled downpipe 8 ln either direction. However, where `the loads leading to fuel burners (not shown) in a burner '35 are subject to great fluetuatien, it has been. box 9 opening into the vcombustion chamber 9'. 35

found preferable to control the fuel ow and The 110W 0f gas through the pipe 5 and main damper control apparatus of the boiler in timed "I can be manually controlled by the variousV steps, in order to avoid periodic rapid variations valves illustrated. It is preferable, however, to

of decreasing amplitude on opposite sides of the control this flow automatically by the apparadesired constant pressure, and to preclude postuS illustrated generally in Figure 1 and in 40 sible overiiring or undermine of furnaces, not in greater` detail in Figure 2 of the drawings. The

proportion to change in steam demand, if timed automati Control referred t0 comprises a Pair step by step ming is 'not provldedof lamps `IIJ and Il, preferably unfrosted and The main object of the present invention is, operably connected to the mains 2 and' |13 therefore, to provide a pressure control system i photoelectric'cells I4 and I5, respectively; and mth tlmmg elements to mtl/ose Ste-p'by'step a shutter I6, mounted for rotation-between the oPeratlon of the fuel-110W and. damper mecha' lights and the cells, is operated in accordance msm for the purpose of effectmg pressure sta' with pressure rvariationsin the steam `chamber O- bilization in the boilers withoutfimposing rapid s of the systemlg control the tmnsmlsslony of v.

variations in .pressure on .opposite sides of a light from one or the other of the two lamps desired eOnStant DreSSure- I0'and II to the respective cells I4 and I5.

Other objects of the'nveutionfwill become ap- The photoelectrie oeils I4 and` l5 include in parent es the detailed description thereofY protheir circuits the local batteries l1 and lsfwhlch 5.3 eeeds. f energize the electromagnets Il and 2l, respecu These lamps I0 and` II are used to energize 45 2 tively, when light from the lamps |8 and is transmitted to the cells I4 and' I5. The electromagnets I9 and 29'control the movements of switchrods 2| and 22, respectively. The switch rod 2| is normally held by means of a spring 23against a stop member 24; and is adapted, when the electromagnet I9 is energized, to be drawn into contact with a contact terminal 25 on a wire 26. A solenoid 21 lcontrols the operation of a valve` in the high pressure part of the gas supply piping to be described hereinafter.

I'he circuit through the solenoid 21 and switch rod 22 is completed by a branch wire 28 from the main I2 to the pivoted end of the switch rod 22 and by wires 33 and 33 through solenoid 2'1 to the-return main I3. J'Iheswitch rod 22 is connected at its pivoted end to the wire 28 leading from thel main I2, and is normally held in circuit breaking position by a spring 39\ against the stop 3|. When the magnet 29 is energized, it draws the switch rod 22 against the contact 32 at the end of a wire 33 leading to one terminal of an electromagnet 34, the other terminal of which is connected byV a wire 35 to the return.

wire I3. The wire 26 is connected by a wire 36 to one terminal of an electromagnet 31, the other terminal of which is connected by a wire 38 to the return main I3. The wire 33 is tapped by a wire 39 to a brush 48 secured to a support of insulating material 4| xed adjacent a commutator slip ring 42 in constant contact with the said brush. The wire 33 is also tappedby a wire 33' to one terminal of a solenoid 21, the other terminal of which is connected by a Wire 29 to the return wire I3.

A wire 83 connects a secdnd brush 44, mounted on the insulating brush support 9|, to the solenoid 95, the circuit through which is completed by a wire 86 to the return main I3. A wire 41 is tapped from the wire 28 to a brush 48 mounted on an insulated support 99 xed adjacent to a commutator slip ring 59 for the brush'88. A wir 5I connects a brush 52, also mounted on the support 89, to a solenoid 53, the circuit through which is completed by a wire 58 tapped .to the wire 29 leading to the return main I3. .v

'I'he rings 42 and 59 are mounted on a shaft of amotor M supported by a plate 58. A timer switch 51 is also secured to the shaft 55 to be rotated in synchronism with the rings 82 and 58 and this switch and the rings are suitably insulated from each other and from the motor. The switch 51 comprises three conducting segments 58, '59, and 69, mounted on a conducting slipring 6I, and separated by gaps so as to break the circuit intermittently between two brushes 62V and 63 suitably mounted on an insulating support 64. i

The brush 63 rides on the ring 65 while the brush 62 is supported so as to contact 'slidably with the outer periphery of the segments 58, 59,

and 68. The brush 62 is connected by a. wire 66 to' the I2, and brush 63 is connected byv a wire 61 to a wire 68. The electromagnet 31 is normally energized and therefore normally holds a switch rod 69, against the tension of a spring 18, away from a contact terminal 1I at the'end '111e switch rod 69 has its pivotof the I2. ed end connected to the wire 68 ending in a contact 12 arranged in the path of a switch rod 13 which is normally held by the electromagnet 34 out,` of contact with the contact 12 and against the tension of a spring 14.

The solenoids l5, 53 'and 21, when energized,

open valves 1l. 16, and 11, respectively, control' lin accordance with rotation of lever cable |I3 is connected at its upper v'end to the 89 connects the line 18 to one end of the casingv 8| of the valve 15; and a pipe 82 controlled by a valve 83 connects the other end of the casing 8| to one end of a control cylinder 84. A pipe 85, controlled by a valve 86 is connected to one end of the casing 81 of valve 16; and a pipe 81 controlled by valve 88 is connected to the other end of cylinder 84. A pipe 89 controlled by a valve 98 is connected to one end of the casing 9| of the valve 11; and a pipe 92 controlled by a check valve -93 and a needle valve 94 is tapped into the pipe 82.

The pipe 92 is connected, vbetween the valve casing 9| and check valve 83, by a pipe 95 to one end of a cylinder 96 'controlling the flow of gas through a by-pass 91 connected on opposite sides of a butterfly valve 98 to the low pressure main 1. A manually operable valve 99 is arranged in the by-pass 91 in advance of the control cylinder 9B. v'l'.'he needle valves 94 may be operated when desired to cut oii communication between pipes 82 and 92.

A piston |99 reciprocates in the cylinder 84 and operates a.. piston rod I9I which slides through a bearing in a standard |92 suitably supported by the main 1. the rod is pivoted to one end of a. link |83 (see Figure 1) having its other end pivoted to one end of a second link |94 which has its other end xed to a shaft |85. A lever |96 xed to the end of the shaft |95 is connected by cables to the opposite ends of a similarV lever |99 secured to the end of a shaft ||9 extending into a flue I|| of the system and having a damper ||2 suitablysecured thereto. As shown in Figure 1, the levers and I 99 are provided with series of apertures for receiving the ends of cables |81 and |88 to vary adjustment of the damper I2 pivot connecting links |93 and |84 to each other, and has its lower end connected to a bell crank for operating the draft louvres shown in detail) controlling the admission of air to the combustion chamber 9.

The rod |8| -has a pin IIE projecting laterally therefrom, and slidable in a slot IIB formed in a link ||1 having its lower end pivoted to the low pressure main 1. The upper end of link |I1 is pivoted by a. link I|8 to the upper end of a link |I9 having its lower end fixed to a shaft |29 extending across the main 1 and carrying the buttery valve 98. It will be obvious from inspection of Figures 1 and 2that reciprocation of piston |88 in cylinder simultaneouslyvoperates the valve 98 and the damper I|2.

The by-pass pipe 91 has a valve I2| mountedtherein on a. shaft |22 having one end projecting through the side of pipe 91. A lever |23 is adjustably connected at one end, by any suitable securing means such as a set screw |24, to the I5 (not.

The outside end of shaft |22, and is provided with a slot |25 in' which is slidably mountedthe pin |26 projecting laterall;7 from the piston rod |21.

The rod |21 is connected at one end to a piston '|28 reciprocable in the cylinder 96, and slides through a bearing |29 in a bracket |38 and has its free end connected to one end of a cable |3| extending around pulleys |32 and |33 xed to a wall of the combustion chamber. The other end Vof the cable is fixed to the bell crank Ill controlling the burner louvres IIS; and aweight |39 is xed tothe cable |3| between the pulleys and |33.

The cylinder 84 has its opposite endsconnected by relatively small valve controlled exhaust pipes and |36 to ,the low pressure main 1; and the cylinder- 96 is similarly connected by valve controlled pipes |31 and |38 to the by-pass pipe 91.- By this means the gas under pressure in the cylinders exhausts into the low pressure main at such rate as to allow the pressure to build up as required, and also to allow the pressure gas to escape at both ends of the cylinders at a predetermined rate.

The shutter I6 of Figure 2 is shown in Figure 5 as an arm |39 -flxed at its center to the shaft of a Bourdon pressure gauge 4| connected for operation to the steam chamber. S by a pipe f |42 (see Figure 1). The gauge has been modied to adapt it for control of the photo-electric cells by the lamps l0 and I. The usual flexible pressure tube |43 issupported at one end on a hollow standard |44, and has its other end pivoted tothe usual link and gear mechanism for rotating the shaft |40 in accordance with variations plate.

in pressure in the steam chamber S.

The fixed plate |44 takes the place of the usual pressure gauge dial, andv is provided with two 'narrow slots |45 and |46l formed in alignment in a line below and parallel to the diameter of the 'I'he back |41 of the gauge is provided with comparatively large holes |48\and |49 to permit light transmitted through the slotsl |45 and |46 to pass freely through the gauge, which, as shown in Figure l, is interposed between the lights and photoelectric cells.

'I'he arm |39 has its opposite44 ends provided with enlargements |50 and |5| adapted by rotation of shaft |40vto swing across the slots |45 and |46, respectively. The lower edge of the enlargement |50 is parallel to and slightly spaced from the upper edge of the slot |45 when the f of the system will become apparent by a. description of the operation of the apparatus as a whole. Let it be assumed that the boiler plant is idle. Fires are ilrst lit in the boiler in the usual manner by hand operatiom. and the valve 99 in the by-pass 91 is set to by-pass enough gas to take care of the average minimum of fuel required when the butterfly valve` |2| -is opened. This buttery valve |2| is adjusted relative to its operating lever |23 so that when the piston |28 in the cylinder 96 moves said lever to its closing-v limit, the said butterfly valve is positioned to permit the ow of g as Vthrough the by-pass at the extreme minimum' rate' requiredby the plant.

. The piston |00 in the cylinder 84 of the main fuel line 1 is then caused to move to the full' open position by operating the solenoidvalve 16 by hand. Next, the draft conditions in themain -stack damper' are adjusted by hand and by manual adjustment of the valve 6 in the fuel line until the boiler is brought up to desired .pressure at a desired rate offuel feed.

The enlargement .|5| isv The main switch (not shown) `supplying current to the photo-electric control is then closed and the master damper of the system is opened,

and the automatic photo-electric control as@` sume: operation as an ordinary fireman. Ars'the valve 6'has been opened to supply the maximum gizes the electromagnet |9 and permits the spring 23 to draw the switch rod 2| away from the contact 25, thereby breaking the circuit through the electromagnet 31 and permitting the spring 10 to draw the switch rod ,61 against the contact 1| and close the circuit through the brushes 62 and 63 on the motor control switch 51 to start the motor M in operation. Y

'I'he motor M rotatesv the shaft 55 until one of the contact lugs on the commutator ring 42 contacts with the brush 44 to complete the circuit to the solenoid valve 15. The magnets 53 and 21 are therefore deenergized, valves 1G and 11 close, and valve 15 remafis open and gas under pressure ows through the pipe 85 to the right hand end of the cylinder 84 and forces the piston |00 through a certain distance tothe left in the said cylinder. This movement continues so long as the brush 44 engages one o f the contact lugs on the commutator ring 42. As soon as the brush 44 separates from the contact lug irnmediately under it, the solenoid 45 of the valve 15 is-deenergized and the valve closes and remains closed until thel brush 44 makes contact with the next succeeding contact lug.

Whenthe motor control ring. 51 shall have moved until the brush 62 is 'over one rof the gaps and magnets 34 and 31 again energized, the mot-or stops. It will be noted' that the ,several contact lugs on' the rings 50 and 42 arespaced on the respective rings so as to coincide in angular position on the shaft with, the positions of the notches o n the motor control ring 51. The distance through which the piston |00 travels may be determined by adjustment of the various needle valves 83, 88, 94, etc. so as to govern the rate of flow of gas under pressure to the cylinder 84;

and, also by thewidth of the wiping surface on the contact lugs on the -commutator rings 50 and 42.

In an actual installation, it is found that the travel of piston 00 in its cylinder can be adjusted so that it will travel 1/7 of its stroke duringthe period o'f contact of the brushes with the lugs on eitherof the commutators 50 or 42. This stroke can be altered very readily in a few moments by changing the rate of flow of gas to the cylinder through adjustment of the needle valves provided. 'It has been found that the travel can be limited to l/20 of the full stroke of the piston in the cylinder in the two and onehalf seconds the lugs on the commutators are ;in contact with the brushes 44 `and 52, without changing the lugs.

As soon as the lug on the ring 42 passes out of contact with the brush 44, the. solenoid valve 15 closes and the piston comes to rest when the admitted gas under pressure escapes through the bleeder exhausipipes |35 and |36 connecting the opposite ends of the cylinder ,84 to the low pressure main 1. By this operation, the fuel supply to the Ifurnace has been decreased and a period of rest follows during which the commutator ring 42 travels through a part of the revolution until another lug comes in contact with the brush 44. This period of rest gives the boiler time to respond to change of temperature in the furnace.

Let it be assumed that the pressure in the boiler is still too high when the brush contacts with one of the lugs on the commutator. The circuit will again be completed to the solenoid magnet of the valve 15 and the piston |00 will be moved another step toward the left of the cylinder, thereby further reducing the flow of gas through the main 1 past the butterfly valve 98 and by the same amount as in the previous step; and another pause ensues for the same interval of time to give the boiler time to react to the changed condition of ow of gas. Let it be vassumed that at this setting of the valve 98 suflicient gas will pass through the low pressure main 1 to maintain a constant pressure at the desired point in the boiler. Then, the solenoid 45 will be deenergized to close valve 15 and the pressure become balanced on both sides of the piston |00 in the cylinder B4, and thev piston will remain in that position until the demand on the boiler changes.

In' the meantime, the circuit will be closed through the solenoidsA 34 and 31 and the motor M will come td' rest as soon as the control ring 51 arrives at such position that one of its gaps is located beneath the contact lug 62. This condition, of course, has been brought about by the change in fuel flow in the low pressure main 1 creating a change in pressure in the steam chamber so that the pressure gauge is operated to restore the arm |39 to its normal position in which both lamps transmit their light to both photo-electric tubes, and have therefore moved the switch rod 2| to close the circuit through the line 26.

Assume that the load on the boiler again decreases the pressure will have time to rise in the same manner described. The light will again be occluded from the photo-electric tube I4, gas will be further reduced, and the damper further closed as in the previously described case. Let it be assumed that the load goes down to such an extent that the valve 98 goes to its full closed position, as shown in Figure 2, and yet the pressure still slightly exceeds the desired point. The by-pass valve |2I will then be opened during the time the solid part of the arm |39 is over the slit |46 on the dial of the pressure gauge. It will then be apparent that if the amount of gas being by-passed in the valve |2| in open position is excessive, as soon as the arm |39 moves further in a clockwise direction until the slit |52 registers with the slit |46 in the pressure gauge dial, both photo-electric tubes`will again be en=, ergized and the circuit will become completed to the auxiliary solenoid valve 11. The opening of valve 11 causes fuel to ow from the manifold 19 through pipe 95 to the -right hand side of piston |28 in cylinder 96, thereby moving piston- |28 and valve |2| against the pull of weight |34 to decrease still further' the ow of fuel from the main 1 through the by-pass 91 to the burners.

The condition of pressure on both sides of the piston |00 will be balanced and the piston will remain at the extreme left end of its travel. Just enough gas is allowed to `iiow through the check valve 93 to assure that the piston will remain in that position; but gas will be admitted to the right hand end of the .cylinder 96 which operates the by-pass valve |2|, and as soon as this pressure builds up the piston will move to the left raising the counterweight |34 (see Figure l) and closing the louvres in front of the burner chamber 9'. This will reduce the gas flowing in the by-pass to a pointnot in excess of the minimum requirement rof the plant at any time.

Therefore, it will be seen that the next change in boiler load will cause the pressure to drop and it will be apparent that the rst thing to happen will be that the by-pass valve |2| will open; and as soon as the steam demand rises to justify it, the piston |00 in the cylinder 84 will start operating in step by step movements to adjust the fuel flow and damper regulations to meet the new requirements. It will be evident that at this point, the mechanism will cause the louvre in front of the burners to open whenever the valve 98 in the main gas line is in any position but the closed one.

'Ihe operation of the valve 16 is controlled by the photoelectric tube I5 and is substantially the same as the operation of the valve 15. However, the valve 16 'is used to increase the flow of fuel through the main 1 by moving the piston |00 toward the right of its position as shown in Figure 2. The opening and closing of the valve 16 is effected by the commutator ring 50 in precisely the same manner as the `opening and closing of the valve 15 is effected by the commutator ring 42.

Wher the arm |39 of the pressure gauge rotates counter-clockwise in accordance with pressure conditions in the steam chamber, it covers the slot |45 and deenergizes the photoelectric tube l5, thereby deenergizing the magnet 20. The switch arm 22 is then pulled by' the spring 30 into'open circuit position against the stop 3|. This circuit break deenergizes the magnet 34 and permits the spring 14 to draw the switch arm k13 into conducting contact with the contact point 12. The motor M will then be energized through the main I2, wire 13', the switch arm 13, contact point 12, wires 61 and 61' to the motor M, and through the motor M to the return line I3.

The rotation of the motor, of course, rotates the commutator ring 50; and when the ring 50 reaches such position as to close the circuit across the brushes 48 and 52, the circuit is closed through the solenoidv 53 of the valve 16 to effect the opening of said valve with the consequent admission of fuel lto the left hand side of the piston |00 as shown in Figure 2. The circuit through this `valve 16 is effected through the main |2, wire 28, conducting switch arm 2|, contact 25, wire 26, wire 41, brush 48, commutator ring 50, brush 52, wire 5|, solenoid 53, wire 54, and wire 29 to the return line I3.

The left hand step by step operation of the piston |00 under the control of the valve 16 is effected in precisely the same manner as a `similar operation of the piston |00 by the valve K15 in the opposite direction.

o It is to be noted that the solenoid 21 is connected in the circuit of the solenoid 53, except that it is connected before the timing unit and will remain energized so long as light vis admitted through the slot |46. Whenever the solenoid 21 becomes deenergized by occlusion of s light through the slot |46, the counterweight `to move to the left in the cylinder SB'and |34 causes a maximum predetermined flow of fuel in the by-pass pipe v91 by pulling the piston |28 to the right hand end of the` cylinder 96.

With continued rise in pressure, the arm |39 continues to move in clockwise direction, indicating that a further reduction `of fuel to the furnace is required. As previously stated, the solid portion |52 of the arm' |39 below the slot |52, is sufficiently wide to ensure that by the time the slot |52 admits light `to the .slot |45, to reenergize the solenoids 53 and-21, the piston A| will have reached its .extreme travel to the left, and will havereduced fuel iiow'to the lowest set amount through the main 46. 'When the thereby reduce the ow 'of' fuel in the by-pass line 91.

Underv the eendmens just deseribed, fuel will be admitted to the furnace at the lowest rate |39 rotates counterclockwise until light is again' occluded from the slot weight |34 again opens the valve inthe by- .pass line 91 to increase the flow of fuel in this `shutter |39 returns to its initial positionas `shown in Figure `of the drawings, which is the normal desired position, in which operation of the auxiliary by-pass is no longer required.

If the demand continues to increase above the `amount of fuel supplied'when the shutter returns to `normal position, then the arm |39 moves further counterclockwise to occlude light` from the slot |45 by the portion |50 of arm |39. Solenoid` valves 53 and 21 will then be energized, causing the piston 00 to start moving in steps 'to the right in order to increase flow in the main 46, just the same' as `when the ow was. Areduced. Of course, the piston |20 in the by-pass line closes again; but, when fuel is admitted ,to the main line -in steps by the' action of the piston |00, there is no furtheruse for the Aby-pass flow, and the pistonA |00 auto" ment to suit the installation but the master control and timing devices can be standardized for |46 and the counter- J scribed as adapted for pressure control, it is intended to be applied alsoto temperature control, or both pressure and temperature control, when the claims refer to pressure it must be understood that this is for convenience only, and that the invention is to be considered broad understood that even though the device be deenough to include temperature as well aspressure control.

It is, of course, to be understood that the fluid pressure for actuating the piston or equivalent motor need not be derived from a fluid concerned with the generation of the pressure to be controlled as is the case in the present embodiment, but that it may for instancebe derived from a foreign source, such as a water mam.

The invention is not to be considered as limited to the use of photoelectric relays or to any particular type of pressure gauge. In one form of the invention, shown in Figure?, the photoelectric relays have been eliminated, and the pressure gauge has been modied so that the controlling electromagnets |9 and 20 of the system are operated by a wiping contact of the gauge indicator over a series of conducting terminals connected vto the relays |9 and 20 to effect the same result as that disclosed in connection .with the system illustrated fully in Figure 2. Y

vIn the modied form` of the-invention, the switch rods 2| and 22 are held by the springs 23 and 30 against the contact terminals 25 and 32, respectively; and are adapted to be withdrawniro'm these contacts by energization of theelectro-magnetsV I9 and 20. This is merely the reverse of the operation inherent in the system indicated in Figure 2. The wiring connecting the switch rods 2| and 22 and contacts 25 and'32 to the mains 2 and to the various control solenoids, is identical with that shown in Figure 2 of the drawings.

The pressure gauge indicated roughly in Figure 7 is operated by the mechanism shown in Figure 4 of the drawings. In this case, however, the dial |44' is not slotted as in the form shown in Figures 5 andv 6. An indicator |39' is secured to the shaft |40 and the point'of this indicator sweeps over the conductingterminals |53, |54 and |55, suitably insulated from each other and mounted on the plate |44" by means of the strip of insulating material |56. The terminal |53 is connected by wire |51 to one terminal of the electromagnet I9; and a wire |58 connects the other terminal of magnet I9 through a wire |59 tothe battery |60, the other side of which is connected by a wire |6| to the indicator |39. The conducting terminal 5 4 is connected by a wire |62 to one terminal of the electromagnet 20,

' theother terminal of which is connected by the wiref|59 to the battery |60. The conducting terminal |55 is connected by wire |63 to the wire |62 which as previously described is connected to one terminal of the magnet 20.

It will be apparent from inspection of Figure 7 that when the indicator |39 lies between the terminals |53 Yand |54, both cf the electromagnets I9 and 20 are de-energized and the switch rods 2| and 22 remain in contact with the contact terminals and 32. As the indicator |39' moves clockwise across the insulating strip |50, it makes contact successively with the terminals |54 and |55; and in each case energizes the electromagnet 20 to pull the switch rod 22 away from contact 32 and thereby break the circuit through the Wire 33. Movement of the indicator in the opposite direction'over the insulating strip |56 and into contact with the terminal |53 will, of course, energize the electromagnet I9 to pull the switch rod 2| away from contact 25 and break the circuit through the wire 2t.

The operation so iar as controlling the timing -mechanism and solenoid valves illustrated in Figure 2 is concerned are identical with the operation of the same mechanism by the photoelectric relay system shown in Figure 2. It is immaterial just what precise pressure operated structures may be used to control the operation of the magnets I9 and 2D. It will be obvious that the wiping engagement of the indicator |39 with the strip |56 and the conductingY terminals embedded therein should be constructed so as to present as little friction as possible to the movement of the indicator over the strip and to eliminate arcing as much as possible. The battery It@ should be of very low voltage to reduce arcing and a trolley wheel may be mounted on the end of the indicator |39' to reduce. friction between that indicator and the conducting strip. The photo-electrically controlled system is preferred, since it eliminates `objectionable friction and arcing inherent in the positive wiping vcontact control system.

While I have inthe above description disclosed a practical applicationof the invention, it is obvious that the particular system as shown and described, or the details of construction of the several instruxnentalities therein combined, may be varied or modified according to the necessities of use without departing from the spiritA and scope of the invention as claimed.

What I claim is: l. In automatic control of uid pressure, pressure regulating means, photo-electric actuated means responsive to one or another of selectively controlled light beams for moving said pressure regulating means in a plus or minus direction fwith respect to the value of the pressure to be regulated responsive to one or' another of`selectively controlled light'beams, means movable in response to variations in the pressure to be regulated for actuating said photo-electric operated means by the selective occlusion of said light beams, and timing mechanism connected to the rst named means to eiect the movements of the pressure regulating means intermittently in timed steps.

sure regulating means, means responsive to one or another ,of selectively controlled light beams for moving said pressure regulating means in a plus or minus direction with respect to thevalue of the pressure to be regulated and including a iluid pressure actuated element, means for supplying fluid pressure to said element, means movable in response to variations in the pressure to be regulated for differentially varying the operation of the second named means by theselective occlusion of said light beams, and timing mechanismr connected to the rst named means to eiect the movements of'the pressure regulating means intermittently in timedsteps.4

3. `In automatic control of fluid pressure, pressure regulating-means, means for moving said pressure regulating means in a plus or minus direction with respect to the value of the pressure to be regulated, including a fluid pressure actuated element, individual means for supplying ud pressure selectively .with plus or minus effect to said uid pressure actuated element,

2. In automatic control of fluid pressure, pres.

` and a rotatable shutterl responsive to the fluid pressure to be regulated having its ends normally adjacent to and clear of said slots, said shutter alternately occluding one or the other of said slots when rotated from its normal position.

5, In automatic control of iiuid pressure as claimed in claim 3, the light beam occluding means including a screen having lslots -therethrough, a rotatable shutter having its ends normally adjacent to and clear jof said slots but to alternately ccclude one or the other of said slots in other positions of said shutter, and a vessel in communication with the pressure to be regulated and deformable under variations of said pressure and operatively connected to said shutter.

6. In automatic control of iluid pressure, pressure'regulating means, meansfor moving said pressure yregulating means in a plus'or minus direction with respect tothe value of the pressure to be regulated, including a uid pressure actuated element, individual electrically operated means for supplying iiuid pressure selectively with plus or minus eiect to said fluid pressure actuated element, said means being in circuit with an adequate power source, and including relays, photo-electric circuits for said relays eachjincluding a light sensitive current varying element, means for projecting a light beam toward each element, means movable in response to variations in the pressure to be regulated for selectively occluding one or the other of said lightbeams, and timing mechanism connected to the first named fmeans to eect the movements of the pressure regulating means intermittently in timed steps.

7. In automatic control of uid pressure, pressure regulating means, means for moving said pressure regulating means in a plus or minus direction with respect to the value of the pressure to be regulated, including a fluid pressure actuated element, electrically operated valves communicating with a source of lfluid under pressure and with said pressure actuated element for selectively supplying uid pressure thereto with plus or minus effect, electric oper- `ating means for said valves in circuit with an adequate power source and including relays,

photo-electric circuits for said relays each including a light sensitive circuit varying element, vmeans for projecting a' light beam toward each element, means movable in response to variations inthe pressure to beregulated for selectively occluding one or the other of said light the rst named means to eect the movements of the pressure regulating means intermittently in timed steps.

8. .In automatic control of fluid pressure, pressure regulating means, and means for moving the same in a plus or minus direction with respect to the value of the pressure to be regubeams, and timing mechanism connected to lated, ixmiuliim;V s. cylinder and piston, the latter having a normal intermediate position in said i cylinder,J valves communicating WithY a source of liluid pressure and with said cylinder on oppog site sides of said piston, electricalmeans for operating said valves in circuitl with an adequate power source and with relays, photo-electric circuits for said relays, each including a light sensitive current varying element, means forv projecting a light beam toward each element, means movable in response to variations in the pressure to be regulated, for selectively occluding one orthe other or neither` of said light beams,

and timing mechanism connected to the first named means to veiiect the movements of thepressure regualting means, intermittently in timed steps. t

9. In automatic control of uid pressure, pressure regulating means, means for moving said pressure regulating means in a plus or minus ldirection with respect -to the value of the pres- 'sure to be regulated including a uid pressure actuated element, individual means for-supplying uid pressure -selectively with plus or minus eiIect to said fluid pressure actuated element, photo-electric circuits for each viluicl pressure supplying means, each including a light sensi- 'tive current varying element, means for projecting mechanism connected to the rst namedl means to eiect the movements of the pressure regulating means, intermittently in timed steps.

10. Automatic uid pressure control system including a steam boiler and a conduit for feeding fuel under pressure -to the furnace of said boiler,

, said conduit including a reducing valve, means for regulating the flow of fuel to said boiler for controlling combustion conditions in the furnace of said boiler, a fluid pressure motor for actuating said regulating means, valves communicatng with said fuel feed conduit on the highpressure side of said reducing valve for supply-` ing fiuidunder, pressure selectively and intermittently with plus or minus effect to said fluid pressure motor, said motor having bleed passages exhausting into said conduit on the low pressure side of said reducing valve, electrically actuated means for operating said valves, said means being in circuits which include an adequatepower source, and relays, photo-electric circuits for said relays, each including a li'ghtlsensitive current varying element, means for projecting a light beam toward each element, and light beam occluding ,means including xed screen having apertures registering with the axes of said light beams, a rotatable shutter having slots adapted simultaneously to register with said slots in one position of lsaid shutter but 'to alternately occlude one or the other of said slots in other positions of said shutter, and a vessel in communication with the steam boiler, and deformable' under variations of boiler pressure, operatively connected to said shutter.

--EDWmLDENNIa j 

